Photosensitive elements containing formazans



United States Patent PHOTOSENSITIVE ELEMENTS CONTAINING FORMAZANS Thisinvention relates to use of formazans in photosensitive elements forphotography.

Formazans that are useful according to the present invention are a classof compounds having the formulas wherein each of R and R represents amember selected from the group consisting of aryl and substituted aryl.R represents a member selected from the group consisting of aryl,substituted aryl, nitro, alkyl containing 1 to 18 carbon atoms, and Hand X represents dialkoxydiphenyl.

An object of the present invention is to provide photographic elementsfor use in photography comprising at least one layer which contains aformazan compound of the class defined above.

Spectra of compounds of the class defined above are characterized byrather broad absorption bands in the visible region. Changes ofsubstituent groups R R and R in the class of compounds cause variationof absorption maxima over a considerable range. This is illustrated inTable l which shows absorption maxima of some typical formazans.

According to the present invention, formazans of the class defined aboveare incorporated in at least one layer of a photosensitive element foruse in photography.

A preferred embodiment of the invention is a photographic elementcomprising a photosensitive silver halide emulsion layer which hasincorporated therein an antifoggant consisting of at least one formazancompound of the class defined. Following are examples which describe inmore detail this preferred embodiment.

EXAMPLE 1 A high-speed, sulfur and gold sensitized bromoiodide emulsionwas prepared and coated upon a cellulose acetate film support byconventional procedures. For a control sample, no forrnazan was added tothe emulsion. For a test sample, tn'phenylformazan was added to the "iceemulsion prior to coating in a proportion of 30 mg. per mole of silverin the emulsion. Silver coverage was 432 mg. per sq. ft. and gelatincoverage was 978 mg. per square foot. The control and test samples werethen exposed on an Eastman 1B sensitometer by conventional procedure andthen processed for five minutes in Kodak DK-SO photographic developer.The samples were then fixed, washed and dried. The control sample hadrelative speed of and fog density of 0.18. The test sample had relativespeed of 71 and fog density of 0.17.

Control and test samples were prepared as just described but wereincubated for one week at F., 50% relative humidity before exposure anddevelopment. The control had relative speed, of 59, fog density of 0.42.The test sample had relative density of 65, fog density of 0.27.

EXAMPLE 2 Control and test samples were prepared and tested as inExample 1 but with various formazans added before coating as shown inTable 2. For these samples silver coverage was 460 mg. per sq. ft. andgelatin coverage was 1.04 gm. per sq. ft. The letter reference to theformazan antifoggant corresponds to letter enumeration in Table 1.

Table 2 Exposed Fresh Exposed After Forruazau Formazan IncubationAntifog Conc., Sample No. gant Mg. per

(Table l) Mole Ag Rela- Fog Rela- Fog tive Density tive Density SpeedSpeed Control (l-(i) 0 100 49 1 A 30 52 .36 30 42 38 3 43 39 9 43 35 367 36 30 43 37 0 100 65 3 71 45 30 71 42 3, 000 50 39 F-ormazans of theclass defined are effective antifoggants when incorporated atconcentrations from about 3 to about 3000 milligrams per mole of silverin silver halide layers.

Although the examples show photographic elements having only onephotosensitive silver halide emulsion layer, this invention includeselements having more than one photosensitive emulsion layer, for examplecolor films, in which at least one of such layers contains a formazan ofthe class defined. In some embodiments of the invention it may bedesirable to employ a mixture of the formazans defined above as anantifogging agent for silver halide films.

These formazans have other utility in photographic films and plates inaddition to their use as antifoggants in the photosensitive emulsionlayer, for example formazans are useful dyes for filter and antihalationlayers.

The invention has been described with reference to certain preferredembodiments, but it will be understood that variations and modificationscan be made within the scope of the invention defined in the followingclaims.

We claim:

1. A photosensitive element for use in photography comprising aphotosensitive silver halide emulsion layer which contains as anantifogging agent at least one formazan compound having the formulaselected from the group consisting of wherein each of R and R representa member selected from the group consisting of aryl and substitutedaryl, R3 represents a member selected from the group consisting of aryl,substituted aryl, alkoxy, nitro, alkyl containing 1 to 18 carbon atoms,and H and X represents dialkoxy biphenylene. i

2. A photosensitive element as defined in claim 1 wherein theconcentration of formazan compound in said emulsion layer is in therange from 3 to 3000 milligrams per mole of silver in the layer.

3. A photosensitive element as defined in claim 1 wherein said formazancompound is 1,5-diphenyl-3 ethoxycarbonylformazan.

4. A photosensitive element as defined in claim I wherein said formazancompound is 1,5-dipheny1-3-nitro formazan.

5. A photosensitive element as defined in claim 1 wherein said formazancompound is 3,5-diphenyl-1-pphenylazophenylformazan.

6. A photosensitive element as defined in claim 1 wherein said formazancompound is l,1'-(3,3'-dimethoxy- 4,4'-biphenylylene bis 3,5-diphenylformazan) 7. A photosensitive element as defined in claim 1wherein said formazan compound is 1,3,5-triphenylformazan.

8. A photosensitive element as defined in claim 1 wherein said formazancompound is l-(4-acetamidophenyl) -3,5-diphenylformazan.

References Cited by the Examiner UNITED STATES PATENTS 2,160,907 6/1939Richardson 9684 3,050,393 8/1962 MacDonald 9684 3,071,465 1/1963 Derschet al. 96109 NORMAN G. TORCHIN, Primary Examiner.

1. A PHOTOSENSITIVE ELEMENT FOR USE IN PHOTOGRAPHY COMPRISING APHOTOSENSITIVE SILVER HALIDE EMULSION LAYER WHICH CONTAINS AS ANANTIFOGGING AGENT AT LEAST ONE FORMAZAN COMPOUND HAVING THE FORMULASELECTED FROM THE GROUP CONSISITNG OF